Apparatus for and a method of growing thin films of elemental semiconductors

ABSTRACT

An apparatus for and a method of growing thin films of the elemental semiconductors (group IVB), i.e., silicon, germanium, tin, lead, and, especially diamond, using modified atomic layer epitaxial (ALE) growth techniques are disclosed. In addition, stoichiometric and nonstoichiometric compounds of the group IVB elements are also grown by a variation of the method according to the present invention. The ALE growth of diamond thin films is carried-out, inter alia, by exposing a plurality of diamond or like substrates alternately to a halocarbon reactant gas, e.g., carbon tetrafluoride (CF 4 ), and a hydrocarbon reactant gas, e.g., methane (CH 4 ), at substrate temperatures between 300 and 650 Celsius. A stepping motor device portion of the apparatus is controlled by a programmable controller portion such that the surfaces of the plurality of substrates are given exposures of at least 10 15  molecules/cm 2  of each of the reactant gases. The chemical reaction time to complete the growth of an individual atom layer is approximately 25×10 -6  second.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the atomic layer epitaxial(ALE) growth of thin films of semiconductors, but more particularly itrelates to ALE growth of thin films of elemental semiconductors, i.e.,silicon, germanium, tin, lead, and, in particular, diamond.

2. Description of the Prior Art

In conventional epitaxial growth systems such as molecular beam epitaxy,plasma-assisted epitaxy, photo-assisted epitaxy, or chemical vapordeposition, the deposited atoms seek their energetically most favorableposition relative to one another and the substrate. For this to happen,the surface migration velocity of the deposited species must besufficient to provide for the smooth and even, i.e., homogenous, growthof a single crystalline film. Energy is required to promote this surfacemigration velocity. This energy is obtained from the epitaxial processvia substrate heat, plasma or photonic supplied energy, or exothermicchemical reactions. If adequate energy is not supplied, the growth willnot be single crystalline. The absolute requirement for this energyneeded to ensure an adequate surface migration velocity sufficient for amorphologically smooth surface and single crystalline growth limits theminimum temperature at which the film can be grown. As semiconductordevice geometries are increasingly diminishing and dimensionaltolerances are becoming a fraction of a micrometer, the resultantimpurity diffusion created by high growth temperatures can no longer bean accepted mode of operation. Consequently, lower temperaturetechniques must be devised to nucleate and uniformly grow thesemiconductors of interest. The atomic layer epitaxy (ALE) process hasbeen shown to be efficacious in this respect for the processing ofcompound semiconductors, i.e., semiconductors which contain two or moreelements from differing groups (columns) of the periodic table.

The atomic layer epitaxy (ALE) process, as far as could be determined,was first disclosed in U.S. Pat. No. 4,058,430 to Suntola et. al., filedon Nov. 25, 1975, and issued on Nov. 15, 1977. As disclosed in Suntolaet. al., the ALE process was thought to be limited to compoundsemiconductors, but moreover, it was thought to be limited to compoundswherein the bonding energies between like cations and like anions wereeach less than that of the cation-anion bonding energy. More recently,however, it has been shown that other compounds, e.g., gallium arsenide(GaAs), are also amenable to ALE growth. The ALE process has been shownto have significant advantages in growing uniform layers of epitaxialthin semiconducting films of compound materials and in intrinsicallyexcluding unwanted impurities from these films. As far as is known,however, the ALE process, with or without modifications, has never beenused in the prior art to grow thin films of elemental semiconductors. Afortiori, the concept of using the ALE process for the growth of thinfilms of elemental semiconductors, at first glance, would seeminappropriate because in the traditional ALE process, the growthcyclically alternates between the growth of the cation and the anionspecies. Consequently, there is a need in the prior art to adapt the ALEprocess to the growth of thin films of elemental semiconductors, e.g.,group IVB (where there are no well defined anion and cation species),while maintaining the traditional attributes of the ALE process.

Artifact diamond, an elemental semiconductor, has been sought for over100 years. While artifact diamond crystals have been produced since the1950's, thin films of diamond have only recently become available. Evenso, thin films of diamond of semiconducting quality have not beenobtained in sufficient quantities to be economically feasible, i.e.,they are simply laboratory curiosities. The primary reason for this hasbeen that the diamond surface reconstructs with double carbon, i.e., C═Cor pi, bonds which leads to graphitic inclusions. Virtually all of theprior art methods of nucleating, synthesizing and growing diamond filmshave used high dilutions of atomic hydrogen (obtained from hot filamentsor plasmas) to terminate the carbon bonds on the diamond surface toprevent the unwanted double pi bond reconstruction of the diamondsurface. Unfortunately, atomic hydrogen bonds very tightly to thediamond surface and is not easily replaced by carbon from a hydrocarbongas source. The result is inhomogeneity and multiple phase boundarieswherein the crystallites of diamond generally form at variousorientations and in the morphology of abrasive sandpaper. Diamondsynthesized in this manner also contains impurities from the hotfilament or plasma chamber. Such material is not suitable forsemiconductor purposes. Consequently, there is a need in the prior artto produce thin films of diamond of semiconducting quality byeliminating graphitic inclusions and process induced impurities, but yetin an economically viable fashion.

To continue, the presence of large quantities of hydrogen during thegrowth of diamond films has been thought to be absolutely necessary.Without it, diamond films exhibiting the definitive 1332 inversecentimeter RAMAN line have not been grown. Without large quantities ofhydrogen, dangling C═C (pi) bonds have formed on the diamond surface.Hydrogen terminates the dangling carbon bonds and prevents the unwantedpi bonding. Hydrogen is also thought to be responsible for the absenceof morphologically smooth single crystalline films. The reason for thisis that the hydrogen binds to the diamond surface with a bondingstrength greater than that of a diatomic C--C (sp³) bond as listed inthe TABLE below. Accordingly, excited carbonaceous radicals compete withatomic hydrogen for the available carbon dangling bond sites on thegrowing diamond surface. Since the lowest free energy state isrepresented by the hydrogen termination of the diamond surface and notby termination with a carbonaceous radical or a carbon atom, it isindeed amazing that diamond grows at all using the prior art methods.

                  TABLE                                                           ______________________________________                                        CHEMICAL BOND STRENGTHS OF ELEMENTAL                                          SEMICONDUCTORS RELATED TO ALE GROWTH                                          Bond Description   Bond Strength (Kcal/mol)                                   ______________________________________                                        Br--Br             46.08                                                      C--Br              95.6                                                       C--N               174                                                        C--O (diatomic)    256.7                                                      C--O (as oxygen on diamond)                                                                      86                                                         C═O            174                                                        C--C (diatomic)    83                                                         C--C (diamond)     144                                                        C--H               99                                                         C--F               117 (107)                                                  C--Cl              78                                                         C--Si              104                                                        Cl--Cl             57.87                                                      Cl--Pb             73                                                         F--F               37.72                                                      F--Si              126                                                        F--Cl              61.4                                                       F--Sn              77                                                         F--Pb              75                                                         Ge--Ge             65                                                         Ge--O              159                                                        H--C               80.9                                                       H--Cl              103.1                                                      H--F               135.8                                                      H--H               104.18                                                     H--I               71.4                                                       H--Si              74.6                                                       H--Ge              76.5                                                       I--I               36.06                                                      O--H               111                                                        Pb--O              99                                                         Si--O              192                                                        Si--Si             76                                                         Sn--O              133                                                        Sn--Sn             46.7                                                       ______________________________________                                    

Currently, four different basic methods are used to grow diamond filmsin the prior art. The methods are (1) the hot filament method (with orwithout electric field bias), (2) the immersed plasma method, (3) theremote plasma method, and (4) the photo-assisted growth method.Variations and combinations of these methods are also used. All of themethods use carbonaceous gases highly diluted in hydrogen and,therefore, are costly (other methods using ion beams have notdemonstrated definitive RAMAN lines). In all of the foregoing methods,only a fraction of the hydrogen molecules are decomposed into atomichydrogen and these resultant hydrogen atoms are commonly thought toaccomplish several functions. First, they extract hydrogen atoms alreadyattached to the diamond surface by forming molecular hydrogen. This isseen in the TABLE above to be an energy efficient action as the H--Hbond strength exceeds the C-H bond strength. Second, other hydrogenatoms attach to the nascent dangling carbon surface bonds. If this isnot accomplished prior to the denudation of a second and adjacent carbonlattice site, the possibility exists for the formation of an unwantedC═C pi surface bond. Fortunately, there is a time constant associatedwith the formation of unwanted C═C bonds from the nascently formedadjacent dangling carbon surface bonds. This time constant is not knownwith great accuracy; however, it is thought to be generally sufficientto allow for the probability of attachment to the dangling surface bondof an sp³ -bonded methyl or an acetyl radical necessary for thecontinuation of diamond growth. Third, the atomic hydrogen is capable ofsevering a nascent C--CH₃ surface bond to form a methane molecule andleave behind a dangling surface bond. This is the process of methanationwhich is evidenced by the much slower diamond growth rate as thecarbonaceous reagent is increasingly diluted in molecular hydrogen.Thus, the probability that a denuded dangling carbon surface bond willbe reterminated by a hydrogen atom is 10⁴ times more probable than itsbeing reterminated by a carbonaceous gas radical. Fourth, the atomichydrogen is believed to "etch" away any unwanted graphite that mayresult when unwanted C═C bonds are formed. It is thus seen that thehydrogen termination of the growing diamond surface prevents unwantedC═C bonds and graphite from forming, but that it is energeticallyfavorable for the diamond surface to remain terminated by hydrogenrather than to grow. Hence, the probability of a continuous diamond filmgrowth uninterrupted by hydrogen "inclusions" is energetically remote. Afurther complication of hydrogen in the growth of diamond is thathydrogen can be incorporated both interstitially (not on lattice sites)and substitutionally (as a replacement for carbon on a diamond latticesite). It is generally thought that the interstitial hydrogen is drivenoff at temperatures above 650 Celsius. Consequently, there is a need inthe prior art to grow single crystalline diamond films in an improvedmanner such that hydrogen inclusion and, hence, grain boundaries areprevented.

OBJECTS OF THE INVENTION

Accordingly, a principal object of the present invention is to grow thinfilms of elemental semiconductors, i.e., silicon, germanium, tin, lead,and, especially diamond, by a modification of the atomic layer epitaxy(ALE) method which shall be referred to hereinafter as theextraction/exchange method.

A corollary object of the above object is to grow the thin films of theelemental semiconductors by cyclically exposing their growth surfaces todifferent reactant gases or by physically cycling the growth surfacesbetween differing reactant gas sources.

Another object of the present invention is to grow each thin film of theelemental semiconductors to a uniform thickness over a large area.

Yet another object of the present invention is to grow singlecrystalline thin films of diamond in such a manner that hydrogeninclusion, and, thus, grain boundaries are eliminated.

Still another object of the present invention is to grow singlecrystalline thin films of diamond so as to prevent the inclusion ofgraphitic defects and process induced impurities.

A further object of the present invention is to grow thin films of theelemental semiconductors, i.e., group IVB, in a homogenous manner withsurfaces that are atomically smooth and morphological.

A corollary object of the above object is to grow single crystallinethin films of diamond wherein the atomically smooth and morphologicalsurfaces are achieved at growth temperatures far below normal, and belowthe temperature at which surface migration velocity can be relied uponto achieve the foregoing.

Yet a further object of the present invention is to grow thin films ofelemental semiconductors wherein substantially 100 per cent nucleationcoverage on each atomic layer thereof is achieved at growth temperaturesbelow which surface migration velocity can be relied upon to promotesingle crystalline growth.

A still further object of the present invention is to grow bothstiochiometric and non-stoichiometric compounds of the elementalsemiconductors of group IVB by the extraction/exchange method accordingto the present invention.

SUMMARY OF THE INVENTION

In accordance with the above stated objects, other objects, features andadvantages, the present invention has as a primary purpose to improvethe fabrication of thin films of the elemental semiconductors, i.e.,silicon, germanium, tin, lead, and, especially, diamond. It has asecondary purpose to synthesize both stoichiometric andnon-stoichiometric compounds of the group IVB elements.

The essence of the present invention is in adapting the atomic layerepitaxy (ALE) process to the growth of thin films of the aforementionedelemental semiconductors. The modified process is termed theextraction/exchange method. In so doing, all of the traditionalattributes of the ALE technology, e.g., layer thickness uniformity overlarge areas and unwanted impurity exclusion, are maintained. Inaddition, adapting the ALE process to the epitaxial growth of thin filmsof diamond also circumvents the unwanted properties of excess hydrogen,i.e., slowing of growth rate and prevention of contiguous films, whileretaining the beneficial properties of hydrogen, i.e., carbon danglingbond termination, prevention of unwanted C═C bonds, and "etching" ofgraphite. Also, the extraction/exchange method of the present invention,permits the growth of non-stoichiometric, artificially structured, groupIVB compounds and provides the general advantages of the ALE technologyto both stoichiometric and non-stoichiometric compounds of the group IVBelements.

Briefly, according to the method of the present invention, two differentsources of reactant gases are chosen for each elemental semiconductor tobe grown. One of the sources contains either hydrogen or a hydride gashaving molecules composed of hydrogen and an atom(s) of thesemiconductor to be processed, e.g., methane (CH₄), silane (SiH₄),germane (GeH₄), stannane (SnH₄), while the other source contains eithera halogen or a halide gas molecules having of a halogen and an atom(s)composed of the semiconductor to be processed, e.g., carbontetrafluoride (CF₄), silicon tetrachloride (SiCl₄), germaniumtetrachloride (GeCl₄), stannous tetraiodide (SnI₄). The halogen ischosen such that its bond strength to hydrogen substantially exceedsthat of the elemental semiconductor tetrahedral bond strength, e.g.,H-F>C--C, that of the semiconductor to hydrogen bond strength, e.g.,H-F>C-H, and that of the semiconductor to halogen bond strength, e.g.,H-F>C-F. The halogen is also chosen such that it is too large to readilydiffuse into the semiconductor being grown, e.g., fluorine for diamondor silicon carbide (SiC), chlorine for silicon and silicon germaniumcompounds, bromine for germanium and germanium-tin compounds and iodinefor tin and/or lead. Accordingly, hydrogen-halogen extraction processes,inter alia, are used to form elemental semiconductor bonds of thediamond-building crystal structure type in real time and in a mannerwhich for diamond precludes adjacent lattice site C═C bonds fromforming, and, thereby precluding unwanted graphite inclusions. Theextraction/exchange method, according to the present invention,alternatingly extracts the respective surface-terminating hydrogen orhalogen atom(s), abstracts a halogen or hydrogen atom(s) from animpinging gas molecule, forms a new hydrogen-halogen gas molecule, e.g.,H-F, and in exchange reterminates the nascently denuded surface atomwith the gaseous radical formed by the immediately preceedingabstraction. The method of the present invention also precludesgrain-inducing hydrogen terminated carbon inclusions by ensuring thatall hydrogen is cyclically extracted by a halogen. To reiterate, thepresent method is applicable to the ALE growth of silicon, germanium,tin and lead, as well as diamond, and to the ALE growth of the group IVBcompounds.

BRIEF DESCRIPTION OF THE DRAWINGS

The previously stated objects, other objects, features and advantages ofthe method according to the present invention will be more apparent fromthe following more particular description of the preferred embodimentstaken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic block diagram representation of a growth apparatussuitable for carrying out the method according to the present inventionincluding a partial sectional view of a growth reactor chamber portionthereof and a diamond or other substrate to be processed;

FIG. 2 is a transverse sectional view of the growth reactor chamberportion of FIG. 1 taken along line 2--2 thereof in the direction of thearrows;

FIG. 3a is a three lattice constants (atoms) wide schematic diagramdepiction of the hydrogenated [111] surface of, e.g., the diamondsubstrate of FIG. 1, which occurs in the processing of thin films ofdiamond semiconductors in the first step of the method according to thepresent invention;

FIG. 3b is the three lattice constants (atoms) wide schematic diagramdepiction of FIG. 3a illustrating the first CF₄ molecule impinging onthe surface thereof, which occurs between the first and second steps ofthe method according to the present invention;

FIG. 3c is the three lattice constants (atoms) wide schematic diagramdepiction of FIG. 3b after the surface thereof is completely terminatedwith CF₃, which occurs in the second step of the method according to thepresent invention;

FIG. 3d is the three lattice constants (atoms) wide schematic diagramdepiction of FIG. 3c illustrating the first CH₄ molecule impinging onthe surface thereof, which occurs between the second and third steps ofthe method according to the present invention; and

FIG. 4 is a functional block diagram illustrating the essential steps ofthe method according to the present invention, the functional blockdiagram also being useful in understanding the operation of theinvention and the growth apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2 as viewed concurrently, a growth apparatus 10for performing the extraction/exchange method (modified ALE method),according to the present invention, is shown. As will be explainedhereinafter in the section entitled "Statement of the Operation," thegrowth apparatus 10 can be used to grow single crystalline diamond thinfilms and amorphous or polycrystalline thin films if desired. Thin filmsof the group IVB semiconductors, i.e., silicon, germanium, tin and leadcan also be grown. The foregoing are the so-called elementalsemiconductors. In addition, stoichiometric and non-stoichiometriccompounds of the group IVB elements may also be grown by a variation ofthe method according to the present invention. Stoichiometric compoundsare those binary compounds wherein the number of atoms per unit volumeof one material is equal to the number of atoms per unit volume of theother material. Non-stoichiometric compounds are compounds not having aone-to-one ratio of their atoms per unit volume. The judiciousapplication of this approach permits the synthesis of artificiallystructured group IVB materials exhibiting predetermined bandgaps between0 and 5.5 electron volts (ev).

As better shown in FIG. 1, the growth apparatus 10 includes a growthreactor chamber 12 having a plurality of substrates 14 (the thickness isexaggerated for clarity), upon which the desired thin film is to begrown, secured to a pedestal 16. For purposes of the present invention,the growth reactor chamber 12 is cylindrical and would typically be 8inches in diameter and 12 inches in height. Each one of the plurality ofsubstrates 14 would typically be 2 inches in diameter. Integrallyaffixed to the pedestal 16 is a shaft 18 which is sealably and rotatablyaffixed via a seal/bearing 20 to the growth reactor chamber 12. Astepper motor device 22 is operatively connected to the pedestal shaft18 for rotation of the pedestal 16 in the direction indicated bydirectional arrow 24. The stepper motor device 22 includes a positionsensor (not shown) for sensing the position of the pedestal 16 relativeto a first reactant gas sub-chamber 26, a first vacuum sub-chamber 28, asecond reactant gas sub-chamber 30 or a second vacuum sub-chamber 32.The aforementioned sub-chambers 26, 28, 30 and 32 are integrally affixedto the growth reactor chamber 12 (see FIG. 2). A programmable controller34 receives position information from the stepper motor device 22 and,in turn, drives it according to a predetermined timing and switchingsequence. The programmable controller 34 is also operatively connectedto a substrate heater device 36 for maintaining the temperature of theplurality of substrates 14 within a predetermined range. The substrateheater device 36 includes a temperature sensor (not shown) for sensingtemperature information which is fed back to the programmable controller34. The programmable controller 34, in turn, drives the substrate heaterdevice 36 so as to maintain the temperature within the predeterminedrange. The temperature at which the plurality of substrates 14 aremaintained depends upon which material is being grown.

Still referring to FIGS. 1 and 2 as viewed concurrently, a first highcapacity vacuum pump 38 and its associated control valve 40 are bothoperatively connected to the top of the growth reactor chamber 12 via apipeline 42. The pipeline 42 connects to the growth reactor chamber 12via a tailpipe 44. The tailpipe 44 is integrally affixed to each of thesub-chambers 26, 28, 30 and 32 so as to form a portion thereof. A firstplurality of ventholes 46 are configured in the tailpipe 44 so that theyexit into the first vacuum sub-chamber 28. Likewise a second pluralityof ventholes 48 are configured in the tailpipe 44 so that they exit intothe second vacuum sub-chamber 32. These ventholes allow the first highcapacity vacuum pump 38 to better maintain the proper operatingpressures in the aforementioned vacuum sub-chambers, i.e., at loweroperating pressures than the pressures in the reactant gas sub-chambers.

Referring now to FIG. 1 alone, the growth apparatus 10 further comprisesa second high capacity vacuum pump 50 and its associated control valve52. Both are operatively connected to the bottom of the growth reactorchamber 12 via a pipeline 54. Likewise, a high vacuum purge pump 56 andits associated control valve 58 are operatively connected to the bottomof the growth reactor chamber 12 via a pipeline 60. As shown, theaforementioned pumps and their associated control valves are operativelyconnected to the programmable controller 34 and, thus, are operatedaccording to a predetermined timing and switching sequence. Thispredetermined timing and switching sequence for the production ofdiamond thin films, for example, is disclosed in FIG. 4, whichillustrates the essential steps of the method, according to the presentinvention. FIG. 4 will be discussed hereinafter in the section entitled"Statement of the Operation."

To continue, and still referring to FIG. 1 alone, a purge gas container62 containing a purge gas, e.g., dry molecular hydrogen (H₂), and itsassociated control valve 64 and flow controller 66 are operativelyconnected to the top of the growth reactor chamber 12, i.e., to thetailpipe 44, via a pipeline 68 such that each of sub-chambers 26, 28, 30and 32 and, accordingly, the plurality of substrates 14 can be floodedwith the purge gas. As shown, a first reactant gas container 70containing a reactant gas, e.g., a halide group IVB gas such as CF₄ orSiCl₄ for a substrate 14 of diamond or silicon, respectively, and itsassociated control valve 72 and flow controller 74 are operativelyconnected to the top of the growth reactor chamber 12 via a pipeline 76.Hence, in accordance with the predetermined timing and switchingsequence, the first reactant gas subchamber 28 and, accordingly, the oneof the plurality of substrates 14 therein can be flooded with the firstreactant gas. Likewise, a second reactant gas container 78 containing areactant gas, e.g., a hydride group IVB gas such as CH₄ or SiH₄ for asubstrate 14 of diamond or silicon, respectively, and its associatedcontrol valve 80 and flow controller 82 are operatively connected to thetop of the growth reactor chamber 12 via a pipeline 84. Hence, inaccordance with the predetermined timing and switching sequence, thesecond reactant gas sub-chamber 30 and, accordingly, the one of theplurality of substrates 14 therein can be flooded with the secondreactant gas.

As illustrated in FIG. 1, the programmable controller 34 is alsooperatively connected to each of the associated control valves and flowcontrollers 64 and 66, 72 and 74, and 80 and 82, respectively.Accordingly, the timing sequence for diamond ALE growth, ALE growth ofgroup IVB materials and the stoichiometric and non-stoichiometric growthof certain materials to be described hereinafter can be automated toimprove the efficiency and yield of thin film products, according to thepresent invention.

STATEMENT OF THE OPERATION

As shown in FIGS. 1 and 2, the growth apparatus 10 has been configuredto efficiently and effectively carry-out the method according to thepresent invention in an automated fashion. However, the present methodneed not be automated in order to be successfully performed. A simplyconfigured well known gas flow-type ALE reactor (not shown) having asingle chamber suitable for processing only a single one of theplurality of substrates 14 at a time can be used to carryout the methodof the present invention. It should be mentioned that if the gasflow-type ALE reactor is used, halide molecules (first reactant gas) mayadhere to the surface of its single chamber and tend to desorb. Thisdesorption may occur during the hydride (second reactant gas) cycle andinterfere with the exchange reaction in such a manner that only a fewcycles may be successfully completed. The foregoing problem will beeliminated substantially if the inside surfaces of that type of gasflow-type ALE reactor are coated with polytetrafluoroethylene (which isalso known as "TEFLON", a trademark of the E. I. duPont de Nemours &Company, Inc.). The problem of desorption is not evident when the growthapparatus 12 is used to carryout the method of the invention. Thisadvantage is created, inter alia, by configuring the growth reactorchamber 12 to comprise the separate first reactant gas sub-chamber 26,the first vacuum sub-chamber 28, the second reactant gas sub-chamber 30and the second vacuum sub-chamber 32. The first and second reactant gassub-chambers 26 and 30 are each dedicated to use by the first and secondreactant gases, respectively, and are also separated by the first andsecond vacuum sub-chambers 28 and 32. As will be discussed in moredetail hereinafter, this configuration provides excellent isolationbetween the steps of the method involving the reactant gases andprovides for differential pressures between adjacent sub-chambers.

The following examples are illustrative of the method according to thepresent invention of the ALE growth of the elemental semiconductors(diamond, silicon, germanium, tin, lead, and combinations thereof).These examples are not intended to limit the scope of the presentinvention.

EXAMPLE 1

By referring to FIGS. 1, 2 and FIGS. 3a-3d, the general sequence andchemical reactions for diamond ALE growth can best be understood. Forsingle crystalline diamond growth which is necessary for semiconductingelectron device grade diamond, the plurality of substrates 14 chosen canbe single crystalline diamond as depicted by the lattice schematicdiagram(s) for diamond of FIGS. 3a-3d. However, single crystallinesubstrates having lattice constants closely matched to that of diamondcan also be used. Examples are boron doped nickel, copper, berylliumoxide and boron nitride. If single crystalline diamond films are notessential, e.g., for use as optical windows, mirrors, or in tribology,amorphous or polycrystalline substrates of any of the above materialscan be used. In addition, a substrate material that forms a carbide canalso be used for polycrystalline diamond films, e.g., silicon, titaniumand tungsten. Still other non-lattice matched substrates may be used ifthey are first scratched with diamond powder.

If the plurality of substrates 14 are of high purity, i.e., less than 10parts per million of foreign inclusions, their surfaces are subjected toa standard degreasing in trichloroethane, acetone, and/or ethanol,followed by "piranha" (organic removing) cleans (H₂ SO₄ and H₂ O₂ )followed by a standard "RCA clean" such as is routinely used in thesemiconductor industry ("RCA" is the trade name of the Radio Corporationof America). The "RCA clean" technique is described in W. Kern,"Cleaning Solutions Based on Hydrogen Peroxide for Use in SiliconSemiconductor Technology", RCA Review, Vol. 31, p. 187 (1970). Thesecleaning steps are followed by an HF dip immediately prior to insertioninto the growth reactor chamber 12. If the plurality of substrates 14are not of high purity, they must be annealled at high temperature todrive out volatile species and then subjected to surface cleaning in aplasma such as CF₄. This process must be repeated until impurities canno longer be detected on the surfaces of the plurality of substrates 14.In all cases, the plurality of substrates 14 must be baked for asufficient time and at a sufficient temperature to drive outinterstitial hydrogen. For single crystalline diamond substrates, thebaking temperature should be greater than 650 Celsius for a time greaterthan 30 minutes.

After the HF dip, the plurality of substrates 14 are disposed via a loadlock (not shown) into the sub-chambers 26, 28, 30 and 32 of the growthreactor chamber 12. The load lock (not shown) is then secured and thegrowth reactor chamber 12 is evacuated to a pressure of 10⁻⁸ Torr orless by operation of the high vacuum purge pump 56 and its associatedcontrol valve 58 to evacuate any residual impurities. This condition istypically set for about 5 minutes after which the plurality ofsubstrates are next cleaned (purged) in a hydrogen plasma (plasmaexcited molecular hydrogen, H₂) from the purge gas container 62 toremove any oxide that may have accumulated and to terminate all danglingsurface chemical bonds with atomic hydrogen. The molecular hydrogen(purge gas) from the purge gas container 62 is caused to flow viaopening of its associated control value 64 and activation of the flowcontroller 66 by the programmable controller 34. The flow controller 66is set to allow a purge gas flow of approximately 100 cc/minute. Thispurge gas flow rate is not critical and depends upon the size of thegrowth reactor chamber 12. The purge temperature of the plurality ofsubstrates 14 should be set for diamond. The purge temperature range forthe semiconductor being grown is 300 to 650 Celsius. The preferred purgetemperature is 300 Celsius for diamond which is the lowest temperaturewithin the range. The proper purge temperature is maintained by thesubstrate heater device 36 in cooperation with the programmablecontroller 34. The programmable controller 34 also operates at this timeto activate the second high capacity vacuum pump 50 and open itsassociated control valve 52. The vacuum pump 50 is controlled by theprogrammable controller 34 to maintain a range of purge pressuresbetween 20 and 100 Torr with a preferred pressure of 40 Torr during thepurge operation. In addition, the programmable controller 34 operates toactivate a radio frequency (RF) plasma coil device (not shown forclarity) for a period of 30 seconds to "strike" a plasma of themolecular hydrogen after which the RF plasma coil device is deactivated.In so doing and as previously mentioned, the surfaces of the pluralityof substrates 14 are cleaned of all oxides and terminated in hydrogen,i.e., hydrogenated as shown in FIG. 3a. For purposes of the presentinvention, a coil portion (not shown) of the RF plasma coil device iswrapped around the upper portion (top half) of the growth reactorchamber 12. The coil is typically 3/8 inch diameter copper tubing spaced1/2 inch apart. A RF generator portion (also not shown) of the RF plasmacoil device exites the coil with 1 kW of RF energy centered in the 13.56MHz band. In the next step, the flowing molecular hydrogen from thepurge gas container 62 is cut-off by operation of the programmablecontroller 34 on the control valve 64. Then the growth reactor chamber12 is evacuated of molecular hydrogen by operation of the high vacuumpurge pump 56 and its associated control valve 58. Care must be taken soas not to expose the surfaces of the plurality of substrates 14 tooxygen. Accordingly, a high vacuum or flowing dry hydrogen environmentis required. In the present method, a high vacuum environment is used.The high capacity vacuum pumps 38 and 50 maintain the vacuum environmentneeded in the growth reactor chamber 12.

Referring to FIGS. 1, 2 and 3b, the first high capacity vacuum pump 38is activated and its associated control valve 40 is opened by operationof the programmable controller 34. Similarly, the control values 72 and80 are opened and their respective flow controllers 74 and 82 areactivated by the programmable controller 34 to set the gas flow rates ofthe corresponding first and second reactant gas containers 70 and 78each to 10 cc/minute. The gas flow rates are not critical, but must besufficient to ensure that 10¹⁵ molecules/cm² contact all portions of thesurfaces of the plurality of substrates 14 in the reactant gassub-chambers 26 and 30. For the processing of diamond substrates, thereactant gas in the first reactant gas container 70 is carbontetrafluoride (CF₄ ) and the reactant gas in the second reactant gascontainer 78 is methane (CH₄). The temperature of these gases and thepreviously mentioned purge gas, H₂, is nominally room temperature. Forpurposes of the present invention, the gas flow controllers 66, 74 and82 may be of the conventional hot filament type wherein the filamenttemperature and hence its resistence is a function of the gas flow rate.

Consequently and in turn, the hydrogen terminated surface of each of theplurality of substrates 14 is exposed to CF₄. The minimum exposure timeis dependant on the surface temperature, which is controlled, asaforementioned, by the programmable controller 34 in concert with thesubstrate heater device 36 such that all of the surface-terminatinghydrogen is extracted by chemical processes from each surface. At agrowth temperature of 600 Celsius and at a pressure of 40 Torr, theexposure time is typically 600 milliseconds. The maximum exposure timeis only limited by system background contamination. In an ultra highvacuum compatible system with "five nines" pure CF₄ , the maximumexposure time can be several minutes. During this CF₄ exposure, severalchemical reactions occur. As shown in FIG. 3b, each surface terminatinghydrogen atom "transfers its allegiance" to a fluorine atom on a CF₄molecule. The fluorine atom attached to the CF₄ molecule in turn"transfers its allegiance" to the extracted hydrogen atom to form agaseous molecule of HF which is evacuated by the vacuum pumps 38, 50 and56. This leaves a surface atom with a dangling bond and a CF₃ radical inclose proximity to each other. Each are the closest neighbors of theother. As such, the dangling carbon bond of the nascent CF₃ radicalbonds to the nascent dangling surface carbon bond. The energy requiredto break the F atom from the CF₄ molecule is approximately 107 kCal/mol.The energy required to denude the crystalline diamond carbon surface ofits hydrogen termination is approximately 99 kCal/mol. The total energyrequired for bond breaking is thus 206 kCal/mol. The energy liberated informing the HF molecule is approximately 135 kCal/mol and the energyliberated in attaching the CF₃ radical to the dangling surface carbonatom is approximately 144 kCal/mol. The total energy liberated in thisextraction/exchange cycle is thus 279 kCal/mol. The net energy liberatedin this cycle is thus 73 kCal/mol and the cycle is seen to beexothermic. One gas molecule entered into the reaction and one wasevacuated. Thus, negligible evaporative cooling occurs. After thecompletion of this step, the surface of each of the plurality ofsubstrates 14 will have grown by exactly one atomic layer of carbon,i.e., a chemically self-limiting reaction and each surface will beterminated in CF₃ radicals as shown in FIG. 3c. Additional CF₄ moleculesdo not react with the surface because of the self-limiting nature of thereaction as there is no longer any hydrogen present to initiate suchreaction.

After being cycled through the first vacuum sub-chamber 28 to remove anysurplus physisorbed CF₄ molecules, each of the CF₃ terminated surfacesof the plurality of substrates 14 is, in turn, now exposed to CH₄. Theresult of the first such CH₄ molecule is shown in FIG. 3d. Again theexposure time is dependent on the surface temperature. At the growthtemperature of 600 Celsius, exposure time need not exceed 600milliseconds. During this cycle, three of the four hydrogen atoms areabstracted from the CH₄ molecule by surface fluorine atoms requiring 283kCal/mol. These hydrogen atoms attach to three surface-terminatingfluorine atoms on three adjacent CF₃ radicals as illustrated by thefirst such event in FIG. 3d. Formation of the 3 HF molecules (not shown)liberates approximately 405 kCal/mol. FIG. 3d illustrates the firstextraction of the three F atoms from the three adjacent CF₃surface-terminating radicals. The bond breaking extraction requiresapproximately 321 kCal/mol. The dangling bonds on the three (now) CF₂terminating radicals bond with the three dangling bonds from thenascently denuded (now) CF radical liberating approximately 432kCal/mol. Total energy required in bond breaking is approximately 604kCal/mol while that liberated in bond making is approximately 837kCal/mol. The cycle is exothermic by approximately 233 kCal/mol. Foreach CH₄ molecule entering the reaction, 3HF gas molecules (not shown)are created and evacuated by the vacuum pumps 38, 50 and 56. Negligibleevaporative cooling occurs by this process. After all of the availablefluorine sites have been replaced by CH₃ radicals, the surfaces of theplurality of substrates 14 will again appear as in FIG. 3a and noadditional CH₄ reactions will occur, i.e., the reaction is chemicallyself-limiting and again exactly one atomic layer of carbon will havebeen grown. Sequencing the plurality of substrates 14 through the secondvacuum sub-chamber 32 to desorb physisorbed CH₄ molecules completes thiscycle. The sequential cycling of the plurality of substrates 14 throughthe first and second vacuum sub-chambers 28 and 32 ensures that anyphysisorbed boundary layers of the CF₄ and CH₄ reactant gases areremoved, i.e., evacuated, prior to entry into their respective adjacentfirst and second reactant gas sub-chambers 26 and 30. Accordingly, eachsurface of the plurality of substrates 14 at the end of this cycle islike that of FIG. 3a from whence the method began. If additional atomiclayers are to be grown, the sequential cycling of the plurality ofsubstrates 14 may be repeated. It should be noted that the order ofexposure of the plurality of substrates 14 to the two reactant gases isnot critical to the method except as explained hereinafter.

Consequently, ALE growth of diamond is carried out using alternatingexposure to halocarbons, e.g., CF₄, and hydrocarbons, e.g., CH₄, atsubstrate temperatures between 300 Celsius and 650 Celsius with 600Celsius being preferred. The stepping motor device 22 is controlled suchthat the surfaces of the plurality of substrates 14 are given anexposure of at least 10¹⁵ molecules/cm² of the reactant gases in each ofthe reactant gas sub-chambers 28 and 30. This exposure duration isdependent on gas flow rates, sub-chamber size, and vacuum pumpingcapacity, but seldom exceeds 1 second. The chemical reaction time tocomplete the growth of an individual atom layer is approximately 25×10⁻⁶second.

EXAMPLE 2

ALE growth of silicon is carried out using alternating exposure togaseous compounds of silicon and halogen, e.g., SiCl₄ and silicon andhydrogen, e.g., SiH₄, at substrate growth temperatures between 240Celsius and 350 Celsius with 325 Celsius being preferred. Timing andexposure are similar to Example 1 above.

EXAMPLE 3

ALE growth of germanium is carried out using alternating exposure togaseous compounds of germanium and halogen, e.g., GeCl₄, and germaniumand hydrogen, e.g., GeH₄, at substrate growth temperatures between 200Celsius and 320 Celsius with 290 Celsius being preferred. Timing andexposure are similar to Example 1 above.

EXAMPLE 4

ALE growth of tin is carried out using alternating exposure to gaseouscompounds of tin and halogen, e.g., SnBr₄, and tin and hydrogen, e.g.,SnH₄, at substrate growth temperatures between 100 Celsius and 260Celsius with 200 Celsius being preferred. Timing and exposure aresimilar to Example 1 above.

EXAMPLE 5

Pb is grown in a manner similar to the procedure shown for Sn in Example4 above wherein the gases would be PbI₄ and PbH₄. The substrate growthtemperatures would be between 75 Celsius and 175 Celsius with 170Celsius being preferred.

EXAMPLE 6

Stoichiometric growth of SiC is carried out using alternating exposureto gaseous compounds of silicon and halogen, e.g, SiCl₄, and carbon andhydrogen, e.g., CH₄. Alternatively, CCl₄ and SiH₄ may be used. In eithercase, substrate growth temperatures between 400 Celsius and 600 Celsiusare efficacious with 525 Celsius being preferred. Timing, purging andexposure are similar to Example 1 above.

EXAMPLE 7

Non-stoichiometric compounds of the group IVB elements permit thesynthesis of semiconductors exhibiting predetermined bandgaps over therange of 0 to 5.5 ev. This is useful for lowering the unwanted darkcurrent (noise) in optical detectors or otherwise maximizing deviceefficiency. The growth of non-stoichiometric compounds requires that thegrowth apparatus 10 of FIG. 1 be modified to include an additionalreactant gas means. This additional reactant gas means can be added ateither of the pipelines 76 or 84. For purposes of the present invention,the additional reactant gas means could include a container, and itsassociated control valve and flow controller. Of course, the exposuresequence will be controlled by the programmable controller 34. Thenon-stoichiometric growth of Si.sub..8 C.sub..2 is carried-out using anexposure sequence as follows:

a. SiF₄

b. SiH₄

c. SiF₄

d. SiH₄

e. SiF₄

f. CH₄

g. (repeat the above sequence) at substrate growth temperatures between300 Celsius and 500 Celsius with 330 Celsius being preferred. Timing,purging and exposure are similar to Example 1 above.

EXAMPLE 8

Stoichiometric growth of GeSi is carried out using alternating exposureto gaseous compounds of germanium and halogen, e.g., GeBr₄, and siliconand hydrogen e.g., SiH₄, at substrate growth temperatures between 275Celsius and 400 Celsius with 310 Celsius being preferred. Timing,purging and exposure are similar to Example 1 above. The preferred purgetemperature is 275 Celsius.

EXAMPLE 9

Non-stoichiometry growth of Si.sub..4 Ge.sub..6 is carried out using anexposure sequence as follows:

a. SiCl₄

b. SiH₄

c. GeCl₄

d. GeH₄

e. GeCl₄

f. SiH₄

g. SiCl₄

h. GeH₄

j. GeH₄

k. (repeat the above sequence at a substrate growth temperature between275 Celsius and 400 Celsius with 310 Celsius being preferred.

It should be noted that four separate gas sources are required for sucha stoichiometric ratio whereas only two gas sources would be requiredfor a Si.sub..2 Ge.sub..8 stoichiometric ratio similar to Example 7above. Other timings, purgings and exposures are similar to Example 9above.

EXAMPLE 10

Stoichiometric SnGe growth is carried out using alternating exposures togases of tin and halogen, e.g., SnI₄, and germanium and hydrogen, e.g.,GeH₄, at substrate growth temperatures between 180 Celsius and 290Celsius with 270 Celsius being preferred. Timing, purging and exposureare similar to that of Example 1 above. Non-stoichiometric GeSn growthis accomplished by means similar to that illustrated in Examples 7 and 8above. The preferred temperature is 180 Celsius.

EXAMPLE 11

Stoichiometric growth of GeC is accomplished in a manner similar toExamples above except that GeF₄ is substituted for SiF₄.

EXAMPLE 12

Non-stoichiometric growth of the materials of Example 11 above isaccomplished in a manner similar to Example 9 above except that CF₄ issubstituted for SiCl₄ and CH₄ is substituted for SiH₄.

FIG. 4 is a functional block diagram which illustrates, in a summaryfashion, the essential steps of the method according to the presentinvention as established by Examples 4 through 5. In addition, thefunctional block diagram of FIG. 4 contains the processing and decisioninformation needed to program the programmable controller 34 (see FIG.1). For purposes of the present invention, the programmable controller34 can be an analog or digital computer which has been programmed toperform the method steps exemplified by Examples 1 through 5 and,accordingly, automatically fabricate the products thereof. Toautomatically perform the method steps exemplified by Examples 6 through12, the growth apparatus 10 of FIG. 1 has to be modified to accommodatethe additional reactant gas sources. The programmable controller 34 ofFIG. 1, then, would have to be programmed to sequence the reactant gassources according to Examples 6 through 12. The timing and exposurefactors are similar to Examples 1 through 5. It should be mentioned thatthe products of Examples 1 through 12 can be manually fabricated just aseffectively as they can be automatically, but clearly not aseconomically or efficiently.

Referring again to FIGS. 1, 2 and 4 as viewed concurrently, thepre-cleaned plurality of substrates 14 are disposed into the growthreactor chamber 12 via a load lock (not shown) as indicated by processblock 86. In sequence, process block 88 indicates activation of the highvacuum purge pump 56 and opening of its associated control valve 58 bythe programmable controller 34 to quickly evacuate the growth reactorchamber 12 to a pressure of 10⁻⁸ Torr or less for a period of at least 5minutes to rid the growth reactor chamber 12 of impurities. As indicatedby process block 90, the second high capacity vacuum pump 50 isactivated and its control valve 52 is opened to assist the high vacuumpurge pump 56 in evacuating hydrogen from the growth reactor chamber 12.Next, and as indicated by process block 92, the purge gas (molecularhydrogen) from the purge gas container 62 is caused to flood the growthreactor chamber 12 by opening of the control valve 64 and activation offlow controller 66 by the programmable controller 34. The programmablecontroller 34 also operates to activate the substrate heater device asindicated by process block 94 to set the substrate temperature withinthe purge temperature range of 300 Celsius to 650 Celsius, with apreferred temperature of 300 Celsius.

To continue and as indicated by process Block 96, the RF coil plasmadevice (not shown) is activated by the programmable controller 34 for aperiod of about 30 seconds to "strike" a plasma of the molecularhydrogen such that the surfaces of the plurality of substrates 14 arecleaned of all oxides and terminated in hydrogen. As also indicated byprocess block 96, the RF coil plasma device is then deactivated afterthe 30 second period. Process block 98 indicates the closing of thecontrol valve 64 and the deactivation of the flow controller 66 afterthe purge clean operation. Process block 100 indicates the activation ofthe high capacity vacuum pump 38 and the opening of its associatedcontrol value 40 by the programmable controller 34. The high capacityvacuum pumps 38 and 50 maintain the vacuum environment, e.g., 40 to 400Torr, needed in the growth reactor chamber 12 to carryout the methodaccording to the present invention. The highest pressures are in thereactant gas sub-chambers 26 and 30, and the lowest pressures are in thevacuum sub-chambers 28 and 32. As indicated by process block 102, thesubstrate heater device 38 is reset by the programmable controller 34 tothe proper growth temperature for the material being processed. Asexplained previously, the growth temperatures fall within a usefulrange. Thus, a critical temperature uniformity is not as important as itis in most other growth systems.

To continue, the reactant gases from the reactant gas containers 70 and78 are caused to flow into their respective reactive gas sub-chambers 26and 30 by the opening of the associated control valves 72 and 80 and theactivation of corresponding flow controllers 74 and 82. These actionsare indicated by process block 104. Accordingly, and as better shown inFIG. 2, at this point in time two of the plurality of substrates 14 aredisposed in the reactant gas sub-chambers 26 and 30 under the influenceof corresponding reactant gases. For diamond these gases are CF₄ andCH₄, respectively. As shown, the other two of the plurality ofsubstrates 14 are disposed in the adjacent vacuum sub-chambers 28 and 32which are low pressure regions. As indicated by process block 106, thestepper motor device 22 is activated by the programmable controller 34.The stepper motor device 22 which is operatively connected via thepedestal shaft 18 to the pedestal 16 begins "stepping" the plurality ofsubstrates 14 in such a manner that each one thereof is sequentiallypositioned in, for example, the reactant gas sub-chamber 26, the vacuumsub-chamber 28, the reactant gas sub-chamber 30 and the vacuumsub-chamber 32. Since the plurality of substrates 14 have beenpreviously hydrogenated, any one thereof initially positioned in thesecond reactant gas sub-chamber 30 under the influence of thehydrocarbon gas, e.g., CH₄, will not grow until it is rotated to thefirst reactant gas sub-chamber 26 under the influence of the halocarbongas, e.g., CF₄. It will, of course, grow during its second andsubsequent exposures to the hydrocarbon gas in the second reactant gassub-chamber 30. The process can also start alternately or concurrent atthe reactant gas sub-chamber 30, but as previously mentioned, no initialgrowth will occur therein. Consequently, each one of the plurality ofsubstrates 14 is resident in the aforementioned sub-chambers for aduration of time necessary to expose each surface thereof to at least onmolecular layer of the impinging reactant gases in either of thereactant gas sub-chambers 26 or 30 and/or to vacuum desorb all but onemolecular physisorbed "boundary layer" of the reactant gases from theprevious step(s) so as not to impair the extraction/exchange process.The centrifugal forces generated during the step rotation also act to"desorb" physisorbed molecules. The timing will vary depending upon theflow rates of the reactant gases, the resident pressure and temperaturein the growth reactor chamber 12 and the physical size thereof. Forpurposes of the present invention 600 milliseconds under flow of each ofthe reactant gases and 600 milliseconds each under vacuum desorbing issufficient when the background system pressure is 40 Torr or lower. Thereactant gas steps are self-limiting so that exactly one atomic layerfor each reactant gas cycle is grown on the surfaces of the plurality ofsubstrates 14. Thus, of the four plurality of substrates 14 shown, theone initially residing in the first reactant gas sub-chamber 26 willreceive one atomic layer of growth prior to rotation of the pedestal 16.During the next 270 degrees rotation of the pedestal 16, each one of theother three plurality of substrates 14 will have grown by one atomiclayer. The one of the plurality of substrates 14 that was initially inthe first reactant gas sub-chamber 26 will have received an additionalatomic layer of growth. For each subsequent 180 degrees rotation of thepedestal 16, all four of the plurality of substrates 14 each will growan additional atomic layer. Alternatively, by delaying the flow of thehydrocarbon gas into the first reactant gas sub-chamber 30 until thepedestal 16 has rotated its initial 270 degrees, all four of theplurality of substrates 14 will receive equal atomic layers of growth.Once activated, the stepper motor device 22 is configured to "step"through the required number of complete rotations and then stop(automatic deactivation). As indicated by decision block 108, if moreatomic layers of growth are desired, the stepper motor device 22 isagain activated and the process is repeated. As also indicated bydecision block 108 if no more atomic layers of growth are desired, thegrowth apparatus 1 is secured. This action is indicated by process block110 wherein the flow controllers 74 and 82 are deactivated, the vacuumpumps 38, 50 and 56 are deactivated, the control valves 72, 80, 40, 52and 58 are closed, and the heater device 36 is deactivated by operationof the programmable controller 34. As indicated by process block 112,removal of the finished products from the growth reactor chamber 12completes the process.

To these skilled in the art, many modifications and variations of thepresent invention are possible in light of the above teachings. It istherefore to be understood that the present invention can be practicedotherwise than as specifically described herein and still be within thespirit and scope of the appended claims.

What is claimed is:
 1. A method of atomic layer epitaxial (ALE) growthof a thin film upon a surface of a substrate of an elementalsemiconductor selected from the group consisting of silicon, germanium,tin, lead and diamond comprising the steps of:hydrogenating said surfaceof said substrate; in a first exposing step, exposing said surface ofsaid substrate to a first reactant gas thereby growing thereon a firstlayer, said first exposing step including the steps of resetting thepressure acting upon and the temperature of said surface of saidsubstrate to a growth pressure within a range of growth pressures, andto a growth temperature within a range of growth temperatures,respectively, and then exposing said surface of said substrate to ahalogen-group IVB containing gas; desorbing said first layer on saidsubstrate of all physisorbed species of said first reactant gas; in asecond exposing step, exposing said first layer on said substrate to asecond reactant gas thereby growing thereon a second layer, said secondexposing step including the steps of maintaining the pressure actingupon and the temperature of said first layer on said substrate to saidgrowth pressure and temperature, respectively, and then exposing saidfirst layer on said substrate to a hydrogen-group IVB containing gas;and desorbing said second layer on said substrate of all physisorbedspecies of said second reactant gas.
 2. The method of claim 1 whereinsaid hydrogen-group IVB containing gas for the ALE growth of silicon isSiH₄, of germanium is GeH₄, of tin is SnH₄, of lead is PbH₄ and ofdiamond is CH₄.
 3. The method of claim 1 wherein said hydrogenating stepincludes the steps of:setting the pressure acting on said surface ofsaid substrate to a purge pressure within a range of purge pressures;setting the temperature of said surface of said substrate to a purgetemperature within a range of purge temperatures; exposing said surfaceof said substrate to a purge gas; and striking a plasma in said purgegas to purge clean and, accordingly, hydrogenate said surface of saidsubstrate.
 4. The method of claim 3 wherein said range of purgepressures for purge clean of silicon, germanium, tin, lead and ofdiamond is 20 to 100 Torr.
 5. The method of claim 4 wherein saidpredetermined purge pressure for purge clean of silicon, germanium, tin,lead and of diamond is 40 Torr.
 6. The method of claim 3 wherein saidrange of purge temperatures for purge clean of silicon is 240 to 350Celsius, of germanium is 200 to 320 Celsius, of tin is 100 to 260Celsius, of lead is 75 to 200 Celsius and of diamond is 300 to 650Celsius.
 7. The method of claim 6 wherein said purge temperature forpurge clean of silicon is 240 Celsius, of germanium is 200 Celsius, oftinis 100 Celsius, of lead is 75 Celsius and of diamond is 300 Celsius.8. The method of claim 3 wherein said purge gas is molecular hydrogen.9. The method of claim 8 wherein said plasma of said molecular hydrogenis struck for about 30 seconds.
 10. The method of claim 1 wherein saidrange of growth pressures for silicon, germanium, tin, lead and diamondis 40 to 400 Torr.
 11. The method of claim 10 wherein said growthpressure for silicon, germanium, tin, lead and diamond is 40 Torr. 12.The method of claim 1 wherein said range of growth temperatures forsilicon is 240 to 350 Celsius, germanium is 200 to 320 Celsius, tin is100 to 260 Celsius, lead is 75 to 115 Celsius and diamond is 300 to 650Celsius.
 13. The method of claim 12 wherein said growth temperature forsilicon is 325 Celsius, germanium is 290 Celsius, tin is 200 Celsius,lead is 170 Celsius and diamond is 600 Celsius.
 14. The method of claim5 wherein said halogen-group IVB containing gas for the ALE growth ofsilicon is SiCl₄, of germanium is GeCl₄, of tin is SnBr₄, of lead isPbI₄ and of diamond is CF₄.
 15. The method of claim 1 wherein saiddesorbing steps comprise removing all of the physisorbed species of saidfirst and second reactant gases by vacuum evacuation.
 16. A method ofatomic layer epitaxial (ALE) growth of a thin film upon a surface of asubstrate of a stoichiometric compound of an elemental semiconductorselected from the group consisting of silicon carbide, germaniumsilicide, germanium carbide and tin germanide comprising the stepsof:hydrogenating said surface of said substrate; in a first exposingstep, exposing said surface of said substrate to a first reactant gasthereby growing thereon a first layer, said first exposing stepincluding the steps of resetting the pressure acting upon and thetemperature of said surface of said substrate to a growth pressurewithin a range of growth pressures, and to a growth temperature within arange of growth temperatures, respectively, and then exposing saidsurface of said substrate to a halogen-group IVB containing gas;desorbing said first layer on said substrate of all physisorbed speciesof said first reactant gas; in a second exposing step, exposing saidfirst layer on said substrate to a second reactant gas thereby growingthereon a second layer, said second exposing step including the steps ofmaintaining the pressure acting upon and the temperature of said firstlayer on said substrate to said growth pressure and temperature,respectively, and then exposing said first layer on said substrate to ahydrogen-group IVB containing gas; and desorbing said second layer onsaid substrate of all physisorbed species of said second reactant gas.17. The method of claim 16 wherein said hydrogen-group IVB containinggas for the ALE growth of silicon carbide is CH₄, of germanium silicideis SiH₄, of tin germanide is GeH₄ and of germanium carbide is CH₄. 18.The method of claim 16 wherein said hydrogenating step includes thesteps of:setting the pressure acting on said surface of said substrateto a purge pressure within a range of purge pressures; setting thetemperature of said surface of said substrate to a purge temperaturewithin a range of purge temperatures; exposing said surface of saidsubstrate to a purge gas; and striking a plasma in said purge gas topurge clean and, accordingly, hydrogenate said surface of saidsubstrate.
 19. The method of claim 18 wherein said range of purgepressures for purge clean of silicon carbide, germanium silicide,germanium carbide, and tin germanide compounds is 20 to 100 Torr. 20.The method of claim 19 wherein said purge pressure for purge clean ofsilicon carbide, germanium silicide, germanium carbide, and tingermanide compound is 40 Torr.
 21. The method of claim 18 wherein saidrange of purge temperatures for purge clean of silicon carbide is 240 to350 Celsius, of germanium silicide is 200 to 320 Celsius, of tingermanide is 100 to 260 Celsius, and of germanium carbide is 200 to 300Celsius.
 22. The method of claim 21 wherein said purge temperature forpurge clean of silicon carbide is 300 Celsius, of germanium silicide is280 Celsius, of tim germanide is 240 Celsius, and of germanium carbideis 300 Celsius.
 23. The method of claim 18 wherein said purge gas ismolecular hydrogen.
 24. The method of claim 23 wherein said plasma ofsaid molecular hydrogen is struck for about 30 seconds.
 25. The methodof claim 16 wherein said range of growth pressures for silicon carbide,germanium silicide, tin germanide, and germanium carbide is 40 to 400Torr.
 26. The method of claim 25 wherein said growth pressure forsilicon carbide, germanium silicide, tin germanide, and germaniumcarbide is 40 Torr.
 27. The method of claim 16 wherein said range ofgrowth temperatures for silicon carbide is 400 to 600 Celsius, germaniumsilicide is 275 to 400 Celsius, tin germanide is 180 to 240 Celsius andgermanium carbide is 260 to 500 Celsius.
 28. The method of claim 27wherein said growth temperature for silicon carbide is 525 Celsius,germanium silicide is 310 Celsius, tin germanide is 270 Celsius andgermanium Carbide is 450 Celsius.
 29. The method of claim 16 whereinsaid halogen-group IVB containing gas for the ALE growth of siliconcarbide is SiCl₄, of germanium silicide is GeBr₄, of tin germanide isSnI₄ and of germanium is carbide GeF₄.
 30. The method of claim 16wherein said desorbing steps comprise removing all of the physisorbedspecies of said first and second reactant gases by vacuum evacuation.31. A method of atomic layer epitaxial (ALE) growth of a thin film upona surface of a substrate of a non-stoichiometric compound of anelemental semiconductor comprising the steps of:(1) hydrogenating saidsurface of said substrate; (2) exposing said surface of said substrateto a first reactant gas thereby growing thereon a first layer; (3)desorbing said first layer on said substrate of all physisorbed speciesof said first reactant gas; (4) exposing said first layer on saidsubstrate to a second reactant gas thereby growing thereon a secondlayer; (5) desorbing said second layer on said substrate of allphysisorbed species of said second reactant gas; (6) repeating step (2)thereby growing a third layer; (7) repeating step (3); (8) repeatingstep (4) thereby growing a fourth layer; (9) repeating step (5); (10)repeating step (2) thereby growing a fifth layer; (11) repeating step(3); (12) exposing said fifth layer on said substrate to a thirdreactant gas thereby growing a sixth layer; and (13) desorbing saidsixth layer on said substrate of all physisorbed species of said thirdreactant gas.
 32. The method of claim 31 wherein said non-stoichiometriccompound is Si.sub..8 C.sub..2.
 33. The method of claim 32 wherein saidfirst reactant gas is SiF₄, said second reactant gas is SiH₄ and saidthird reactant gas is CH₄.
 34. A method of atomic layer epitaxial (ALE)growth of a thin film upon a surface of a substrate of anon-stoichiometric compound of an elemental semiconductor comprising thesteps of:(1) hydrogenating said surface of said substrate; (2) exposingsaid surface of said substrate to a first reactant gas thereby growingthereon a first layer; (3) desorbing said first layer of said substrateof all physisorbed species on said first reactant gas; (4) exposing saidfirst layer on said substrate to a second reactant gas thereby growingthereon a second layer; (5) desorbing said second layer on saidsubstrate of all physisorbed species of said second reactant gas; (6)exposing said second layer on said substrate to a third reactant gasthereby growing thereon a third layer; (7) desorbing said third layer onsaid substrate of all physisorbed species of said third reactant gas;(8) exposing said third layer on said substrate to a fourth reactant gasthereby growing thereon a fourth layer; (9) desorbing said fourth layeron said substrate of all physisorbed species of said fourth reactantgas; (10) repeating step (6) thereby growing a fifth layer; (11)repeating step (7); (12) repeating step (4) thereby growing a sixthlayer; (13) repeating step (5); (14) repeating step (2) thereby growinga seventh layer; (15) repeating step (3); (16) repeating step (8)thereby growing an eighth layer; (17) repeating step (9); (18) repeatingstep (6) thereby growing a ninth layer; (19) repeating step (7); (20)repeating step (8) thereby growing a tenth layer; and (21) repeatingstep (9).
 35. The method of claim 34 wherein said non-stoichiometriccompound is Si.sub..4 Ge.sub..6.
 36. The method of claim 35 wherein saidfirst reactant gas is SiCl₄, said second reactant gas is SiH₄, saidthird reactant gas is GeCl₄ and said fourth reactant gas is GeH₄.